Device and process for transferring a material web

ABSTRACT

A device for transferring a material web, particularly a web made of paper, board, tissue, or other pulp. In order to transfer the material web and, preferably, a supporting belt from a first supporting surface to a subsequent supporting surface, a pick-up zone to lift the material web off the first supporting surface and a stabilizing zone to stabilize the material web are arranged before the subsequent supporting surface, where vacuum can be applied to the pick-up zone and the stabilizing zone from one vacuum source each. Here, the pick-up zone is sub-divided into at least two pick-up sub-zones across the material web running direction, where the vacuum can be switched on separately in at least one pick-up sub-zone. This invention also relates to a process for transferring a material web performed with the device according to the invention.

BACKGROUND

This invention relates to a device for transferring a material web, particularly a web made of paper, board, tissue, or other pulp. In order to transfer the material web and, preferably, a supporting belt from a first supporting surface to a subsequent supporting surface, the device includes a pick-up zone to lift the material web off the first supporting surface and a stabilizing zone to stabilize the material web before the subsequent supporting surface, where the pick-up zone is limited by sealing mechanisms and the stabilizing zone is limited by a sealing mechanism and a seal, respectively, together with the subsequent stabilizing zone. A vacuum can be applied to the pick-up zone and stabilizing zone from one vacuum source each. This invention also relates to a process for transferring a material web performed with the device according to the invention.

Devices of this kind for web transfer are used in the dryer section of paper machines, for example. These dryer sections usually consist of a number of drying cylinders and suction rolls, each of which are arranged in a row. The material web to be dried, supported in a meandering path by an air-permeable supporting belt, runs from a first drying cylinder to a suction roll and then to a further drying cylinder again. Here, the web must be transferred in the areas between the drying cylinders and the suction rolls. This transfer is effected using special web transfer devices.

Patent application EP 1 788 153 A2, for example, describes a web transfer box with a pick-up zone and a stabilizing zone. In the pick-up zone, the material web and the supporting belt are lifted off the drying cylinder with the aid of vacuum, and in the stabilizing zone that immediately follows, the material web and supporting belt are stabilized by means of vacuum before being transferred to the suction roll. The two vacua in the pick-up zone and the stabilizing zone can be set and adjusted separately in this process.

It is known from the above mentioned EP 1 788 153 A2, among others, that a tail transfer area can be defined in the stabilizing zone at the side edge by means of an air knife. The advantage here is that the transfer vacuum can be increased in the tail transfer area when a tail is transferred, however, this division only applies to the stabilizing zone. The disadvantage here is that vacuum is always applied to the pick-up zone over its entire length across the material web running direction, particularly when the web is being widened. Widening of the web is the process step in which a narrow transfer tail of the material web is widened in stages until the material web has reached the final width required in production. This step is required when starting up a dryer section or after a web break because a full-width material web cannot be threaded in between the drying cylinders and the suction rolls over the entire production width.

Due to the difference between the width of the material web and the width of the pick-up zone when threading in and when widening the web, the vacuum level in the pick-up zone covered by the material web is maintained unnecessarily. This generates high energy costs. In most cases, the vacuum level in the overall system deteriorates, which has a negative influence on functionality.

SUMMARY

The problem thus addressed by the present invention is to create a web transfer device and a transfer process that allows improved web transfer when threading in the web tail and when widening the web.

This problem is solved by a device in which the transfer zone is sub-divided into at least two pick-up sub-zones across the material web running direction, where the vacuum can be switched on separately in at least one pick-up sub-zone. The pick-up zone is sub-divided preferably into 3 to 8 or 4 to 6 pick-up sub-zones.

By sub-dividing the pick-up zone, the sub-zone of the pick-up box to which vacuum is applied can be adapted optimally to the material web width, particularly during widening.

In an advantageous embodiment of the invention, a damper to switch on the vacuum is provided in at least one connecting duct linking a pick-up sub-zone with a vacuum source.

A damper allows the respective pick-up sub-zone to be switched on promptly.

The individual vacua can also be set here by means of a setting damper that is also mounted in a connecting duct. This type of setting damper is a simple and low-cost structure that can be replaced easily in the event of a fault. By mounting it in a connecting duct, the setting damper is easy to access and to actuate.

Advantageously, the individual pick-up sub-zones should be connected to the same vacuum source as this is cheaper. It is also possible, however, to apply the vacuum for the individual pick-up sub-zones using several vacuum sources, which can be smaller in dimension as a result.

The invention also relates to a corresponding process for transfer of a material web, where vacuum is applied separately to pick-up sub-zones arranged across the material web running direction in the pick-up zone.

This process allows optimum adaptation of the pick-up zone to the current material web width.

Advantageously, the vacua in the pick-up sub-zones can be set or adjusted independently of one another. This ensures that the material web is lifted off the first supporting surface at the tangent point.

In an advantageous embodiment of the process, vacuum is applied to the pick-up sub-zones separately from one another when widening the material web. In addition to threading in the transfer tail, it is advantageous to adapt the pressure in the individual pick-up sub-zones during the widening process in order to create an adequate vacuum level.

Here, it is also useful if only those pick-up sub-zones over which the material web passes are placed under vacuum.

There would be no point in applying vacuum to pick-up sub-zones that the material web does not pass over, for example because it has not yet reached its final width. This would only be a waste of suction output from the vacuum source.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which:

FIG. 1 is a schematic side view of a web transfer device according to the invention;

FIG. 2 is a schematic view from above of the web transfer device according to the invention;

FIG. 3 is a view of the web transfer device from above during threading in of the transfer tail and widening of the material web; and

FIG. 4 is a schematic diagram of a further web transfer device according to the invention.

DETAILED DESCRIPTION

The web transfer device 5 according to the invention is shown in FIG. 1. It can comprises a pick-up box 5 and a stabilizing box 7, however it is also conceivable that it comprises only one web transfer box. During operation, a material web 1, coming from the right, is supported on a supporting belt 2 and guided over a first supporting surface 3, which is a rotating and heated drying cylinder in the present example. Then the material web 1 and the supporting belt 2 are lifted off the first supporting surface 3 in the pick-up zone 6. For this purpose, a vacuum is applied to the pick-up zone 6, causing the material web 1 and the supporting belt 2 to be lifted off the first supporting surface 3 by suction. The pick-up zone 6 is sealed off by means of sealing mechanisms 10 and 10′ that run across the machine running direction. The pick-up zone 6 is adjoined by a stabilizing zone 8. In this stabilizing zone 8, the material web 1 and the supporting belt 2 are stabilized by means of vacuum. The stabilizing zone 8 is separated from the pick-up zone 6 by the seal 10′. There may also be a further zone 9, however, between the pick-up zone 6 and the stabilizing zone 8. In this case, this additional zone 9 is limited by the sealing mechanism 10 and the seal 14 across the material web running direction. This additional zone 9 must not necessarily be under vacuum, but can also be open to the machine environment at ambient pressure.

If the additional zone 9 is available, the stabilizing zone is sealed off by the seal 14 across the machine running direction 19.

FIG. 2 shows the web transfer device in a schematic view from above. The reference numerals used in all figures refer to the same items. The figure clearly shows how the pick-up zone 6 is divided into pick-up sub-zones 11, 12, 13 according to the invention. In the present example, the pick-up zone is divided into three pick-up sub-zones 11, 12, 13, where the first pick-up sub-zone 11 is narrower than the second pick-up sub-zone 12. The third pick-up sub-zone 13 is broader than the second pick-up sub-zone 12. The split into 3 pick-up sub-zones is only shown as an example, and it would also be possible to divide the pick-up zone into 2, 4 or more sub-zones. Pick-up sub-zones 11, 12 and 13 can all be the same width or can have different widths, as in the example shown. The pick-up zone 6, and thus also the pick-up sub-zones 11, 12 and 13, can be placed under vacuum from a vacuum source. The flow direction of the air extracted is shown schematically by the flow direction arrows 20. The pick-up sub-zones are each connected via a connecting duct 18 to a suction pipe 24 through which the air from the individual pick-up sub-zones 11, 12 and 13 is extracted by suction.

The vacuum in the individual pick-up sub-zones 11, 12 and 13 can be switched on using the damper 16, and set or adjusted using the setting damper 15. The dampers 16 and setting dampers 15 are located in the connecting duct 18.

FIG. 3 shows the web transfer device according to the invention during the tail threading process and during widening of the material web 1. In the tail threading process, only a narrow strip (tail) of the material web 1 is transferred to the web transfer device. This narrow strip of the material web 1 is limited by the material web edges a and b. The dampers 16 in the second pick-up sub-zone 12 and the third pick-up sub-zone 13 are closed. In this way, only the first pick-up sub-zone 11 is placed under vacuum from the vacuum source 17. As soon as the tail has been threaded in completely, the material web 1 can be widened. In this process, the material web width increases continuously until it has reached the final width as shown by the material web edges a and d. Material web edge c shows the material web 1 during the widening process.

In order to widen the material web 1, vacuum is applied only to those pick-up sub-zones 12, 13 over which the material web 1 passes. Thus, damper 16 in the second pick-up sub-zone 12 is opened when widening begins, setting this zone under vacuum. This guarantees that the part of the material web 1 passing over the second pick-up sub-zone is received reliably by the first supporting surface 3. As long as the material web 1 only passes over the first and second pick-up sub-zones 11 and 12, the damper 16 in the third pick-up zone 13 remains closed. This zone is not placed under vacuum until the material web is wide enough and thus, also passes over the third pick-up sub-zone 13. In this way, vacuum is only applied to those pick-up sub-zones 11, 12, 13 where a vacuum is actually needed to pick up the material web. The dampers 16 can be provided with an automatic control device that opens or closes the dampers depending on the material web width.

FIG. 4 shows a schematic diagram of a further web transfer device according to the invention. Here, not only the pick-up zone 6, but also the stabilizing zone is sub-divided into several stabilizing sub-zones 21, 22 and 23. These stabilizing sub-zones are also adjustable by means of setting dampers 15′, preferably separately from one another. The second stabilizing zone 22 and the third stabilizing zone 23 can be placed under vacuum from the additional vacuum source 17′ by means of the dampers 16′. The stabilizing sub-zones 22 and 23 are switched on by means of the dampers 16′ during widening in the same way as the dampers 16 are switched on in the pick-up sub-zones 12 and 13. In the example shown, the pick-up zone 6 and the stabilizing zone 8 are separated from one another by an additional zone 9. This additional zone 9 is separated from the pick-up zone 6 and the stabilizing zone 8 by the sealing mechanism 10′ and the seal 14, respectively. The pick-up zone 6 and the stabilizing zone 8 can, of course, also be placed directly adjacent to one another.

The embodiments in the drawings only show one preferred embodiment of the invention. The invention also relates to other embodiments in which, for example, the pick-up zone 6 or the stabilizing zone 8 is divided into more than three sub-zones. It is also conceivable that the stabilizing zone 8 is divided into other stabilizing sub-zones 21, 22, 23 than the pick-up zone. Similar to the pick-up sub-zones, the stabilizing sub-zones can also be switched on or adjusted separately.

It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. 

1. A device for transferring a material web from a first supporting surface to a subsequent supporting surface, the device comprising: a pick-up zone adapted to lift the material web off the first supporting surface, the pick-up zone being connected to a vacuum source and being limited by first and second sealing mechanisms, the pick-up zone being sub-divided into at least two pick-up sub-zones across a material web running direction, where the vacuum can be switched on separately in at least one pick-up sub-zone; and a stabilizing zone disposed proximate to the subsequent supporting surface, the stabilizing zone connected to a vacuum source and being limited by the second sealing mechanism and a seal, respectively, and the subsequent supporting surface.
 2. The device of claim 1, wherein the pick-up zone is sub-divided into 3 to 8 pick-up sub-zones.
 3. The device of claim 2, wherein the pick-up zone is sub-divided into 4 to 6 pick-up sub-zones.
 4. The device of claim 1, further comprising a damper provided to switch on the vacuum in at least one connecting duct linking an associated pick-up sub-zone with a vacuum source.
 5. The device of claim 1, further comprising a setting damper mounted in a connecting duct linking an associated pick-up sub-zone with a vacuum source.
 6. The device of claim 1, wherein the individual pick-up sub-zones are connected to the same vacuum source.
 7. A process for transferring a material web from a first supporting surface to a subsequent supporting surface, the process comprising: lifting the material web off the first supporting surface in a pick-up zone using vacuum, the pick-up zone being sub-divided into at least two pick-up sub-zones across a material web running direction, the vacuum being applied separately to the pick-up sub-zones; and stabilizing the material web before the subsequent supporting surface in a stabilizing zone using vacuum.
 8. The process of claim 7, further comprising setting or adjusting the vacua in the pick-up sub-zones independently of one another.
 9. The process of claim 7, further comprising applying vacuum to the pick-up sub-zones separately from one another when widening the material web.
 10. The process of claim 9, wherein only those pick-up sub-zones over which the material web passes being placed under vacuum. 